Will the merc raw water pump draw water up, or does it have to start primed. Id like to fit an inlet/scoop running up a stainless tube on the outside of the transom and then down,into the engine bay to save drilling the hull. There could be a reserve of water/strainer inside the boat, at pump level to act as a primer , but if I can do without it it would be good.
Will this work? anybody done this /ideas? Thanks guys.

The raw water pump does not have to be primed. They do need to run with water in them to keep the impeller blades from coming apart. The few seconds it takes for an empty inlet line to be charged during start up is however permissible by the pump. I believe Merc states they can run for a max of 10 seconds at idle without water, not that I've ever tested that theory. I have never primed them.